Reflecting surface



Nov. 12, 1929. w, CAUGHLAN 1,735,377

REFLECTING SURFACE Filed Oct. 19, 1927 Patented Nov. 12, 1929 IABTEA W.CLUGHLAN, OI OAKLAND, CALIFORNIA BEILIC'IING 81133403 Application meOctober 10,1921. semi in. mass.

My invention has for its object a reflector upon which the rays from asingle source of illumination are reflected but once and are therebyprojected forward as a beam of most intense central illumination withreduced side illumination, and every ray of which beam will be below ahorizontal plane through a common focal point of the reflector or lightsource. A further object is, in a headlight of the character described,a reflector wherein a relatively large portion of the rays emanatingfrom a light source located at a common focal point, are reflected belowand parallel with 16 the horizontal plane and wherein the remaining raysemanating from the lamp are directed downward and over an area belowsaid plane; and all are within a predetermined angle of divergence.

flector having a light source located at a common focal point, the lowersurface of said reflector being formed of differential elements ofsuccessive and varying paraboloids of revolution and whose upper portionis formed by rotatin about an axis of symmetry through sai focus, thefigure formed by the intersection of the lower portion of the reflectorwith a horizontal plane through said axis.

Referring to the drawing.

Fig. 1 is a vertical longitudinal section through one form of thereflector of my invention, and passing throu h the common focus, and onthe line 1-1 0 Fig. 2.

Fig. 2 is a horizontal section throu h the reflector of Fig. 1 and takenon the line 'I1 thereof, and passing through the common focus.

Figs. 1 and 2 show the mathematical con struction and proof ofoperativeness of the reflector of my inventibn.

Fig. 3 is similar to Fig. 2 but showing the lower reflecting surface inplan and with lines shown thereon to indicate certain of the selectedelements or chains of points selected from the family ofparaboloids ofrevolution, and which collectively produce the said surface.

Fig. 4 is a reduced perspective of the lower These objects I attain byproviding a re-' half of the reflector of Figs. 1, 2 and 3 showing indotted lines the pencil of planes and in full curved lines theintersection of said planes with their respective araboloids andtherefore they are all parabo as, and the sum of such infinite numbersof parabolas forms metry. is shown at 11-11.

Other vertical planes are shown at III-- IV-V-VI-VII-VIIIIX. All ofthese vertical planes pencil about the vertical axis The numeral 1indicates generally the lower portion of my reflector and the numeral 2the upper portion thereof.

At 3 is a common focus which is also the light source employed with myreflector.

The construction of my surface is based on the mathematical fact thatthere can be constructed a family of paraboloids, with a common focus 3,whose axes revolve in a horizontal plane about that focus as a pivot,and all whose surfaces pass through a common point 5. As that point isnecessarily at a fixed distance 3, 5, from the common focus 3, it isalso at the same rpendicular distance 4, 6=5, 9 from the directrix ofeach paraboloid of the family. The directrix planes of the family aretherefore all tangent to a right circular cylinder whose axis is theperpendicular 4 5 from the axis of symmetry 3, 4 to the common point 5.and whose radius is the distance 5,Q, from the foot of thatperpendicular to the directrix 7, 9 and'which iswalso the distance 3, 5,of the common point from the common focus.

Let 8 be the vertex and 8-4 the axis of one paraboloid and 50. 51 thetrace of its directrix plane on the horizontal plane II and 7 9 itstrace on the vertical plane of symmetry II-II. With the focus (the lightsource) at 3, I select a convenient point ion the axis and drop aperpendicular 4, 5 and'let3, 5

equal 4, 6. Then 5 is on the surface of the paraboloid, since 3, 5equals 4, 6 equals 5, 9 which satisfies the mathematical law of theparabola. Since 3, 5 is constant for all of the family of paraboloids,whose focus is 3 and which pass through 5, the length 4, 6 is alsoconstant for all, and the directrix planes for all must be tangent to aright circular cylinder having a radius equal to 4, 6, and an axis at4,5.

Let the circular are 20, 6, 22 16 be the trace of that cylinder in thehorizontal plane ll.

Cut the first named paraboloid by a vertical plane llll through the axis4, 6. The parabola 10 will result, and is the center rear line of myreflector. Now revolve the paraboloidal axis inthe horizontal plane Ilon the pivot 3 to any position as 3-17 to represent the axis of anyoneof the family of paraboloids, Fig. 2) and revolve a plane on 4 5 as anaxis, into a position parallel to 3-47 this new plane 111 will cut theparaboloid ina parabola 30, congruent to the generating parabola of thatparaboloid, and is also an element of the surface of my reflector.

Now 4-16 equals 4-6 being the radii of the cylinder, and 314' e uals14-16 (distance of point 14 from the locus and from the directrix.)

In similar manner rotate the paraboloidal axis in a horizontal planeabout 3, and rotate a plane on 4, 5 as an axis, such that the plane andthe axis of its corresponding paraboloid are always parallel. Let 38 beany such point in the horizontal plane where such revolving plane cutsits corresponding paraboiloid. Then 34 will be the parabola cut on thesurface of the paraholoid, and will be one of the elements on thereflector surface! The infinite number of such parabolas so formedconstitute the principal reflecting portion of my reflector lowersurface.

In detail the manner of construction is as follows:

Select a point 4 in the plane 1-1 and a second point 5 below 4, suchthat 4, 5 is at right angles to 3, 4. Choose a point 6 on the line 3, 4produced, and midway between 3 and 6 a point 8. Through the point 8 as avertex, conceive a paraboloid whose directrix is 7 9, and whose focus is3, it will cut the plane II in the parabola 10. See Figs. 1 and. 4.

By the law of the parabola every point thereon will be equi-distant fromthe focus and from the direct-rix. Such a parabola will therefore passthrough the point 5, the distance 3, 5 being equal to 4, 6 equal to 5,9. This parabola, a single element from the aforesaid paraboloid will bethe central element 10 of my lower reflecting surfacesee Figs. 3 and 4.

Midway between 3 and 4 at-12, draw the line 13, 14, see Fig. 2, and with4 as a center describe the circular arc 20--622-16; and continue 4, 14to 16. Continue 13, 3 to 17 on F the line 16, 18, atright angles to 13,17 and at right angles to 4, 16.

The line 16, 18 is tangent at 16 to said arc 20.

At 19 midway between 3, 17 construct a paraboloid of revolution whosefocus is 3, and whose trace is 23 and the trace of whose directrix planeis 18, 16.

The vertical plane through the axis 4, 5 and the point 14 will cut fromthe paraboloid whose trace'is 23 thesingle parabolic line'- projected inplan as 30 of Fig. 3.

From any other point 22 on the said are 20 draw the line 22, 4 andparallel theretof through 3, draw 3, 25. Through the center 25 constructthe paraboloid of revolution" whose trace is 27. on the axis 3, 25.

On 22, 4 lay off the point 28 equi-distant from3 and 22. It will lieupon the paraboloidal surface whose trace is 27.

, In like manner consider an infinite number of paraboloids ofrevolution all having the common focus 3 and all lying upon axes inthe'horizontal plane I-I, that is the plane of Fig. 2, and between thelines 3,17 and 3, 29. The directrix planes of all of said paraboloidsare to be tangent to the curve 20-6 2216.

Now, through the line 4, 5 as an axis pass a pencil of planes 11,111,IV, V, VI, etc-see Fig. 4. Note particularly that the plane lI of theparaboloidal axes is at right angles to the axis of the said pencil ofplanes.

The plane 11 willcut the paraboloid whose axis is 4, 6 in the parabola10.

The plane 111 will cut the paraboloid whose trace is 23 and whose axisis 3, 17 inthe parabola 30 and plane IV will cut the paraboloid whosetrace is '27 and whose axis is 3, 25 in the parabola 32. All of theseseveral parabolas will appear as straight lines in plan Fig. 3. r

The planes V and VI will likewise cut the paraboloids whose axes are 3,33 and 3, 29 in the parabolas 34 and 31 respectively.

There will therefore be cut from this infinite number of paraboloids bythe infinite number of planes whose axis is 4, 5, an infinite number ofparabolas as 10, 30,31, 32 and 34, see Figs. 3 and 4. g Y

.The lower surface of the reflector to the left of the line 13 14 ofFig. 2 will be made up of such an infinite number of parabolas all ofwhich will have the common focus 3 because they are elementspfcorresponding paraboloids whose focii coincide at 3.

Every ray of light emanatin from 3 will therefore be reflected upon saisurface portion in straight lines parallel vwith the plane II and all ofsuch rays will emerge as an illuminating beam between the lines 15 and35 and will all pass through the vertical line 4, 5, and some of thesewill-appear as 50 51, 151, 41 of Fig. 2 and as rays 36, 37, 88 o Thelower surface of the reflector to the right of line 13, 14 of Fig. 2,and below the horizontal plane, II and bounded by 14--5-42-41 is asegment of a single paraboloid of revolution whose trace is 23; and theforward portion of the reflector surface bounded by 13-5-42 4?) islikewise a segment of the surface from the pai'aboloid of vrevolution'whose axis is 14, 29.

If now other planes as VII, VIII, IX, arallel to the plane VI-see Figs.3 and 4- e caused tocut the last named surface, they will likewise cutpanabolas 44, 45, 46 respectively; and on the opposite side of plane IIsimilar parabolas will be cut at 47, 48, 49 by symmetrical planesparallel'to lane III from symmetrical paraboloids, see ig. 3.

As before, all the parabolas 44 to 49 inclusive being elements ofparaboloids whose common focus is 3 will likewise reflect rays of lightoriginating at the focus 3,.below and parallel to the horizontal planeII.

' It follows from the above construction that every ray of lightoriginating at 3 and reflected from the entire lower surface of myreflector will reflect said my in a horizontal plane below the plane IIand through the line 4, 5 and that the aggregate of these rays gill be abeam between the lines 15 and 35 of The upper half of the reflectorabove the horizontal plane II is formed by rotating one-half of thesection shown in Fig. 2, through 180 about the axis 4, 6-see Fig. 1; andby the above analysis it will be seen that every ray of lightoriginating at 3 and reflected by the-upper portion of my reflectorabove the plane II will issue from the reflector below the horizontalplane II.

The illumination produced by my reflector will then be entirely belowthe horizontal plane and between the lines 15 and 35 and with thethereof.

I claim: a

1. A compound reflecting surface having a common focus for allreflecting elements thereon at which focus a source of light is located,the said surface below a horizontal plane through said focus consistingof two rear parts symmetrical about a longitudinal vertical planethrough said focus, the portion of each of said parts adjacent to saidfocus formed of elements from the surfaces of successive increasingparaboloids havin the said common focus and whose axes all lie in saidhorizontal plane and also consisting of two forward parts symmetricalabout said vertical plane and each comprising a surface portion from thegreatest of said paraboloids.

2. A com ound reflecting surface having a common ocus for all reflectingelements thereon at which focus a source of light is located, the saidsurface below a horizontal greatest intensity directly in front planethrough said focus consisting of two rear parts symmetrical about alongitudinal vertical plane through said focus, the portion of each ofsaid parts adjacent to said focus having an axis lying also in saidvertical plane.

3. A compound reflecting surface having a common focus for allreflecting elements.

thereon at which focus a source of light is located, the saidsurfacebelow a horizontal plane through said focus consisting of two rear partssymmetrical about a longitudinal vertical plane through said focus, theportion of eachof said parts adjacent to said focus formed .of elementsfrom the surfaces of successive increasing paraboloids having the saidcommon focus and whose axes all lie in said horizontal plane and alsoconsisting of two forward parts symmetrical about said vertical planeand each comprising a surface portion from the greatest of saidparaboloids, the smaller of said paraboloids having an axis lying alsoin said vertical plane, and all of slaid axes lying within apredetermined ang e.

4. A com ound reflecting surface having a common ocus for'all reflectingelements thereon at which focus a source of light is located, the saidsurface below a horizontal plane through said focus consisting of tworear parts symmetrical about a longitudinal vertical plane through saidfocus, the portion of each of said parts adjacent to said focus formedof elements from the surfaces of successive increasing paraboloidshaving the said common focus and whose axes all lie in said horizontalplane and also consisting of two forward parts symmetrical about saidvertical plane and each comprising a surface portion from the greatestof said paraboloids, and the said surface above said horizontal planegenerated by rotating the intersection of said lower surface with saidhorizontal plane about the line of intersection of said horizontal andsaid vertical planes.

5. A com ound reflecting surface having a common ocus for all reflectingelements thereon at which focus a source of light is located, the saidsurface below a horizontal plane through said focus consisting of tworear parts symmetrical about a longitudinal vertical plane through saidfocus, the portion of each of said partsadjacent to said focus formed ofelements from the surfaces of successive increasing paraboloids havingthe said common focus and whose axes all he 1n said horizontal plane andalso consisting of two forward parts etrical about said vertical-planeand eac comprising a surface portion from the greatest of saidparaboloids, the smaller of said paraboloids havin an 5 axis lying alsoin said vertical plane an the said surface above said horizontal planegenerated by rotating the intersection of said lower surface with saidhorizontal plane about the line of intersection of said horim zontal andsaid vertical planes.

6. A com ound reflecting surface having a common ocus for all reflectingelements thereon at which focus a sourceof light is located, the saidsurface below a horizontal 7 plane through said focus consistingof tworear parts symmetrical about a longitudinal vertical plane through saidfocus, the portion of each of said parts adjacent to said focus formedof elements from the surfaces of suc-v cessive increasing paraboloidshaving the said common focus and whose axes all lie in said horizontalplane and also consisting of two forward parts symmetrical about saidvertical lane and each comprising a surface portion om the greatest ofsaid paraboloids, the smaller of said paraboloids having an axis lyinalso in said vertical plane, and all of sai axes lying within apredetermined angle, and the said surface above said horiso zontal planegenerated by rotating the intersection of said lower surface with saidhorizontal plane about the line of intersection of said horizontal andsaid vertical lanes.

. MARTHA W. CAU m.

